A simple flow cytometric assay for routine paroxysmal nocturnal hemoglobinuria testing based on immature reticulocytes and granulocytes

Validation of a single tube 3-colour immature red blood cell screening assay for the detection and enumeration of small, medium and large paroxysmal nocturnal haemoglobinuria clones by flow cytometry

INTRODUCTION

The reliable diagnosis of paroxysmal nocturnal haemoglobinuria (PNH) by flow cytometry is based on mandatory analysis of the erythroid, neutrophilic and monocytic lineages. In this study, we have evaluated the performance characteristics of a recently published immature red blood cell (iRBC) assay as a potential screening test for PNH by flow cytometry.

METHODS

Intra- and inter-assay imprecision were determined in five replicates of small, medium and large PNH iRBC clones. Analytical and functional sensitivity was assessed by performing spiking tests for five replicates. Thirty healthy donors and 441 PNH patients were tested for evaluation of clinical specificity, sensitivity, positive and negative predictive values.

RESULTS

Coefficients of variation (CV) for intra-/inter-assay imprecision analyses were 1.31/1.50, 3.19/2.61 and 3.99/1.58 for the big, medium and small clone sizes, respectively. Absolute values (100%) were found for both clinical specificity and sensitivity as well as for both positive and negative predictive values. The CV from 5 replicate results for 10 clustered events was 15.7%. The coefficient of determination (r² ), Pearson's correlation coefficient (r) and Bland-Altman mean bias were 0.9436/0.9234/1.7 for PNH iRBC compared to PNH neutrophils and 0.9553/0.9387/2.1 for PNH iRBCs compared to PNH monocytes.

CONCLUSION

Our results confirm very good performance characteristics, high analytical and functional sensitivity, absolute clinical specificity and sensitivity as well as favourable correlation between PNH iRBCs and both PNH neutrophils and monocytes, suggesting that this cost-effective 3-colour iRBC assay can be used as a reliable screening test for evaluation of small, medium and large PNH clones by flow cytometry.

Presentation clinical, haematological and immunophenotypic features of 1081 patients with GPI-deficient (paroxysmal nocturnal haemoglobinuria) cells detected by flow cytometry

A retrospective analysis of presentation clinical, laboratory and immunophenotypic features of 1 081 patients with paroxysmal nocturnal haemoglobinuria (PNH) clones [glycosylphosphatidylinositol (GPI)-deficient blood cells] identified at our hospital by flow cytometry over the past 25 years was undertaken. Three distinct clusters of patients were identified and significant correlations between presentation disease type and PNH clone sizes were evident. Smaller PNH clones predominate in cytopenic and myelodysplastic subtypes; large PNH clones were associated with haemolytic, thrombotic and haemolytic/thrombotic subtypes. Rare cases with an associated chronic myeloproliferative disorder had either large or small PNH clones. Cytopenia was a frequent finding, highlighting bone marrow failure as the major underlying feature associated with the detection of PNH clones in the peripheral blood. Red cell PNH clones showed significant correlations between the presence of type II (partial GPI deficiency) red cells and thrombotic disease. Haemolytic PNH was associated with type III (complete GPI deficiency) red cell populations of >20%. Those with both haemolytic and thrombotic features had major type II and type III red cell populations. Distinct patterns of presentation age decade were evident for clinical subtypes with a peak incidence of haemolytic PNH in the 30-49 year age group and a biphasic age distribution for the cytopenia group.

Integration of Immature Granulocytes Quantification With the Version 2.0 UniCel DxH 800 in the HematoFlow Strategy

OBJECTIVES

Our aim was to define whether the early granulocyte cell marker (EGC%_DxH) parameter might replace immature granulocytes counts obtained by HematoFlow (IG%_HF) and/or manual differential count (IG%_manual).

METHODS

We conducted a study over a 10-day period in February 2014 whereby 402 samples were analyzed for the IG flag. We correlated the EGC%_DxH vs IG%_HF and IG%_manual, identified any discrepant results and finally looked at the impact on our workflow by incorporation of the EGC% into our WBC differential algorithm.

RESULTS

On an initial training set, a receiver operating characteristic (ROC) curve analysis showed a threshold of 0.9% for EGC%_DxH (sensitivity of 91.7%, specificity of 93.5% and an area under the curve of 0.965). Further analysis of the dataset (259 samples) found a correlation of the EGC%_DxH to all our IG% counting methods (r = 0.963). Incorporation of the EGC%_DxH into the WBC HematoFlow differential resulted in a 36% reduction of samples requiring HematoFlow and/or slide review.

CONCLUSIONS

The EGC% generated by the DxH 800 can be easily incorporated into existing HematoFlow and slide review algorithms.